The present invention relates generally to the field of machining operations used in connection with the manufacture of industrial boilers and equipment and, in particular, to a new and useful tool for simultaneously deburring and chamfering holes in a plate workpiece, such as those in a boiler header box tube sheet.
Boiler tube and plug sheets,. referred to hereinafter as "boiler elements", are initially formed with many rough edges or burrs on their interiors which must be removed to finish the boiler elements for use If these burrs are not removed, once the boiler element is placed into service they could break off and be carried into other areas and plug passageways or cause other damage. The boiler elements should also be smooth to avoid undesirable flow characteristics.
Referring to FIG. 1, there is illustrated one known device for deburring such boiler elements, known as a "BUR-BAN" tool, and generally referred to as tool 10, available from the Gruich Tool and Manufacturing Company. This tool 10 is a manually operated cutter, and as shown in FIG. 1, the BUR-BAN tool 10 has a main shaft or body portion 12 of relatively constant diameter D, and a pair of long, slender semi-circular shaft legs 14 connected to the main shaft or body portion 12 with a central gap 16 extending along and between the pair of shaft legs 14. The BUR-BAN tool 10 has cutting edges 18 which are positioned above rounded ends 19 of the shaft legs 14. The cutting edges 18 extend radially outwardly from the longitudinal axis of the tool 10, on the surface of each of the shaft legs 14. Top and bottom surfaces of each of the cutting edges 18 are substantially flat and perpendicular with respect to the shaft legs 14 and the longitude axis of the BUR-BAN tool 10.
In use, the BUR-BAN tool 10 is inserted longitudinally through a hole in boiler element, such as a boiler tube header, to debur the hole. The central gap 16 allows the shaft legs 14 to flex, thereby facilitating insertion and removal of the tool 10 from an opening whose diameter is close to that of the tool 10. The tool 10 is then rotated to cut the burrs off the inside of the boiler element connection. Under certain conditions, the tool 10 must be sharpened frequently, which decreases the speed at which these boiler elements can be deburred. The tool 10 also lacks any means to chamfer the edge of the boiler element connection at the time it is deburred, and it is operated solely by hand.
A modified version of the BUR-BAN tool 10 of FIG. 1 was developed and is illustrated in FIG. 2. This modified tool, generally designated 20, also has a main shaft or body portion 22, a pair of long, slender semi-circular shaft legs 24 connected to the main shaft or body portion 22 with a central gap 26 extending along and between the pair of shaft legs 24, and a pair of cutting edges 28 as before. However, in contrast to the BUR-BAN tool 10, and for a modified tool 20 designed to debur a similar-sized boiler connection, both the main shaft or body portion 22 and the pair of shaft legs 24 of the modified tool 20 have a diameter D.sub.1 which is less than the diameter D of a BUR-BAN tool 10 used for the same deburring application. Further, while the cutting edges 28 of the modified tool 20 are also provided above rounded ends 29 of each of the shaft legs 24 provided on an end portion 30 of the modified tool 20, this end portion 20 has a larger diameter than that of the main shaft or body portion 22, and preferably the same diameter D as used in the BUR-BAN tool 10. The modified tool 20 may also be provided with a reduced diameter opposite end 32 of diameter D.sub.2, to facilitate its use in combination with a drill (hand-held or stationary) or air motor. The reduced diameter D.sub.1 facilitates insertion of the modified tool 20 into a boiler element that is to be deburred, but like the tool 10, it also is incapable of expeditiously chamfering the boiler element connection at the time it is deburred.